Question

a question of CO2 transportation in hemoglobin.

Describe the reaction involved in the transport and the name of the products formed.

Briefly describe how these products promote the released oxygen.

Answer 1

There are three methods by which Carbon dioxide molecules transported from tissue to blood (1) dissolution directly into the blood (2) binding to hemoglobin and (3) carried as a bicarbonate ion.

Major fraction of carbon dioxide molecules (85 percent) are transported bicarbonate ion.

Approximately 20% of carbon dioxide is bound to hemoglobin. Carbon dioxide binds with terminal uncharged amino groups (R-NH2) of amino acid moieties on the globin protein of hemoglobin and form carbaminohemoglobin. Binding of CO2 with hemoglobin is reversible.

CO2 + Hb ↔ HbCO2

Partial pressure of carbon dioxide (pCO2) is responsible for association and dissociation with hemoglobin. Blood leaving the lungs has a lower partial pressure of CO2 than the tissues. CO2 moves to blood and then to RBC from tissue because of its high partial pressure and there hemoglobin bind with CO2. Pulmonary capillaries have high partial pressure of CO2 than alveoli consequently, CO2 get dissociated from hemoglobin.

Effect of carbaminohemoglobin on oxygen binding:

When carbaminohaemoglobin is formed it lower the affinity of hemoglobin for oxygen. This phenomena is known as Bohr effect. When CO2 bind with hemoglobin a decreases in blood pH is occur due to which affinity of hemoglobin for oxygen is decreases. Increase in partial pressures of carbon dioxide make right-ward shifts of the oxygen-hemoglobin dissociation curve. An enzyme carbonic anhydrase converts CO2 into carbonic acid consequently, hydrogen ion released therefore lowering in blood pH occur.